Newer Style Master Cylinder Swap

[ArdWrknTrk]

Be mindful that Bronco's and 150's use a smaller bore MC than 250/350 trucks.

This just caught my attention in the other thread.

[LARIAT 85]

Machspeed wrote

Replaced both the brake booster and upgraded the master cylinder. With my factory lines, it was a direct bolt on with absolutely no modifications required. Only change I had to make was a small adjustment to the booster rod which is very important! I'll be doing a full right up on it soon.

Didn't like the nasty looking booster so pulled it and attempted to clean it up and repaint. It was badly pitted and I struggled to remove the old paint. I also think it was a source so I decided to replace it too. But, the paint on the new booster was garbage so I prepped it and sprayed it with two coats of my favorite epoxy. I still need to to bleed the system, but that won't happen until I get a few other things done.

That looks good.  I think I might have to do this to Lucille someday.  

What is that empty electrical socket for on the left picture, right under the reservoir?

[ArdWrknTrk]

That's for the low fluid warning connector.
You can repurpose the multifunction valve connector to light up the brake warning light if the reservoir gets low.

Standard equipment '87->
Because the later master has the residual pressure check valve incorporated into the rear port of the MC as previously discussed.

[Rembrant]

ArdWrknTrk wrote

That's for the low fluid warning connector.
You can repurpose the multifunction valve connector to light up the brake warning light if the reservoir gets low.

Yes sir, I have it wired in on my 1984 Flareside. The Brake warning lamp will light up if the fluid gets low. The float switch has both NO and NC contacts, so you just have to connect to the correct two.

[Machspeed]

kramttocs wrote

Looks great!
What is that thing tucked behind the speed control unit?

You have a good eye, my friend! It is a siren from an alarm system.

[LARIAT 85]

ArdWrknTrk wrote

That's for the low fluid warning connector.
You can repurpose the multifunction valve connector to light up the brake warning light if the reservoir gets low.

Standard equipment '87->
Because the later master has the residual pressure check valve incorporated into the rear port of the MC as previously discussed.

Multifunction valve connector?  What is that?  Does my truck already have one?

Is it the wire that plugs into my brake proportioning valve?

[ArdWrknTrk]

Ford doesn't call it a proportioning valve, because that's not what it does.

But yes, that thing...

[Machspeed]

LARIAT 85 wrote

ArdWrknTrk wrote

That's for the low fluid warning connector.
You can repurpose the multifunction valve connector to light up the brake warning light if the reservoir gets low.

Standard equipment '87->
Because the later master has the residual pressure check valve incorporated into the rear port of the MC as previously discussed.

Multifunction valve connector?  What is that?  Does my truck already have one?

Is it the wire that plugs into my brake proportioning valve?

I think what you are referring to is the residual pressure check valve which you must have if you have drum brakes. If you have drum brakes, you have this valve. You have the larger master cylinder as I once had and it is built in to your master, not visible as it is on my mod unit. If you had all wheel drums, you would have two built into your master.

I read on one of the forums where some guy doing the same mod as I did, gutted the the residual pressure check valve using it as an adapter. Big mistake!  

[ArdWrknTrk]

The check valve on the frame is to provide a federally mandated loss of pressure warning light on the instrument panel.
This came about in the '60's when they also mandated separate front and rear systems.

The spool moves over, cutting off the loss of fluid while also activating the switch controlling the light.

150's & 250/350's have detents that work opposite. Push in v/s pull out to reset.

Chris (Ctubitus) has section drawings comparing the two over on FTE.

[Rembrant]

ArdWrknTrk wrote

Ford doesn't call it a proportioning valve, because that's not what it does.

But yes, that thing...

Actually, Ford calls it a proportioning valve, at least part of it. I know there's been a lot of debate over this, same as Stepside vs. Flareside, and the starter "solenoid" and Start Relay, etc, but it is what it is I guess.

[ArdWrknTrk]

That's interesting Cory.
All the documentation I've seen calls it a multifunction valve.
But as I've been wrong before, I'll be wrong again.

But what they're calling a "proportioning valve" obviously isn't functioning as a brake bias control, but a residual pressure check valve.

I guess it's just my autistic literalism, but (to me) a "proportioning valve" effects pressure bias, and this as shown can't do that.

[85lebaront2]

Jim. it is also interesting that it was done away with after 1986. The newer master cylinders still have the residual pressure valve for the rear brakes, but no longer have the proportioning function. I removed the valve on Darth when I went to the newer booster and master cylinder. I used an inverted flare union where the RWAL actuator went on the 1990 and gave it and the electronic box to my boss as cores for his 1987 F150 2WD.

[ArdWrknTrk]

Yes, I don't think the multifunction valve would fare well with the hammering it would get from the RABS.

With the warning light moved to the reservoir and the residual pressure check valve moved to the MC there's no reason for it on the Bricknose and later trucks.

[Rembrant]

ArdWrknTrk wrote

With the warning light moved to the reservoir and the residual pressure check valve moved to the MC there's no reason for it on the Bricknose and later trucks.

That’s how my ‘84 is set up, with the lower valve removed. I’m doing the same thing on the ‘80 as well. I cleaned up the old MC from the ‘95 I pulled the frame out of.

[Vic Roma]

Is there an "idiots guide" to the master cylinder upgrade?
I would like to do this on the 84 Bronco, but even with two hands and a flashlight, I'll get lost.

[Gary Lewis]

Not yet, but John/Machspeed said he would do one.  However, if you've read the whole of the thread you've seen that he gave the part number of the one he bought and said it came with the residual pressure valve that is needed.  So it should be a straight master cylinder R&R with the exception that the lines have to be swapped.  And the factory shop manual section on that is at Documentation/Driveline/Brakes and then the Master Cyl's & Boosters tab, the Factory Shop Manual Sections tab, then the Pedal & Master tab.  

[Machspeed]

I can't speak for your this swap into your Bronco, but this was a direct swap into my 86 F150. If your brake lines look like mine, it shouldn't be a problem. From my previous posts in this tread, you will find all the information needed to make the swap, including the part number for the Master Cylinder. You may have to adjust the power booster rod, which you can glean from Youtube.    

[ArdWrknTrk]

Do note that you should get the later reservoir pigtail to indicate fluid loss.
The wiring from the combination valve can be repurposed for this.

[Rembrant]

ArdWrknTrk wrote

Do note that you should get the later reservoir pigtail to indicate fluid loss.
The wiring from the combination valve can be repurposed for this.

Yup. I have mine wired in this way since I removed the combination valve. You could wire them both in if you wanted to. The float switch in the new master has 3 wires...a common, and then N/O and N/C.

[Vic Roma]

Which pigtail fits the BRMC63?